1. Field of the Invention
The present invention relates generally to apparatuses for manufacturing polycrystalline silicon ingots for solar batteries and, more particularly, to an apparatus for manufacturing a polycrystalline silicon ingot for solar batteries which has a door control device using a hinge and is constructed such that silicon which has been melted in a crucible is cooled from the bottom of the crucible to the top thereof.
2. Description of the Related Art
Recently, solar energy generation using silicon solar batteries has been continuously developed owing to its providing various advantages such as being non-pollutive, safe and reliable and has already reached a commercialization stage beyond the experimental stage.
In several countries, for example, the U.S.A, Japan and Germany, solar energy generation of a capacity of several hundreds through several thousands of Kw is being implemented using silicon solar batteries.
At present, solar batteries which are used for solar energy generation are manufactured using a single crystalline silicon film formed by the Czochralski method. However, to continuously produce large quantities of solar batteries through mass production, the cost of manufacturing silicon films will have to be reduced and the productivity will have to increase. Because of such a background, a casting method was proposed in an effort to reduce the cost of manufacturing silicon films for solar batteries.
The manufacture of a polycrystalline silicon ingot for solar batteries using the casting method is characterized by directional solidification.
In detail, after polycrystalline silicon substances are charged into a crucible made of quartz or graphite and are melted, the heat of solution of silicon is removed from the lower portion of the crucible such that the cooling solidification progresses from the lower portion of the crucible to the upper portion thereof. Thus, an ingot having a constant orientation, i.e. an ingot having a columnar structure, is obtained.
Compared to a single crystalline silicon ingot manufactured by the Czochralski method, a polycrystalline silicon ingot manufactured by the above-mentioned method induces a reduction in electric efficiency when manufacturing a solar battery because of grain boundaries formed in the ingot. In addition, because crystals have columnar structures in the direction in which the crystals are grown, general physical properties of the polycrystalline silicon ingot are about 20% lower than that of the single crystalline silicon ingot. However, the casting method of manufacturing the polycrystalline silicon ingot can be easily adapted for mass production (of two or three times larger than that of the Czochralski method of manufacturing the single crystalline silicon ingot) and has superior productivity (two or three times greater than that of the Czochralski method). As well, the method of manufacturing the polycrystalline silicon ingot is relatively simple. Owing to these advantages, the cost of manufacturing the polycrystalline silicon ingot is about ⅓ to ½ of that of the single crystalline silicon ingot.
In typical casting methods known to date, polycrystalline silicon is previously melted in a polycrystalline silicon melting part made of quartz before it is supplied into a graphite crucible. After the melting, the melted polycrystalline silicon is supplied into the rectangular or cylindrical graphite crucible, the entire height of which is maintained at a temperature ranging from 600° C. to 1200° C. Subsequently, a crystal growing process is conducted, thus forming a polycrystalline silicon ingot.
In the case of the above-mentioned conventional casting methods, because cooling solidification rapidly progresses, solidified silicon is prevented from adhering to the crucible. However, there are disadvantages in that contamination of silicon attributable to the crucible is induced, and because heat stress remains, defect concentration is increased and crystal grains are relatively small.